Neutral radical etching of dielectric sacrificial material from reentrant multi-layer metal structures

ABSTRACT

Embodiments are directed to forming reentrant multi-layer micro-scale or millimeter scale three dimensional structures, parts, components, or devices where each layer is formed from a plurality of deposited materials and more specifically where each layer is formed from at least one metal structural material and at least one organic sacrificial material (e.g. polymer) that are co-planarized and a portion of the sacrificial material located on a plurality of layers is removed after formation of the plurality of layers via one or more plasma etching operations or one or more neutral radical etching operations.

RELATED APPLICATIONS

The below table sets forth the priority claims for the instantapplication along with filing dates, patent numbers, and issue dates asappropriate. Each of the listed applications is incorporated herein byreference as if set forth in full herein including any appendicesattached thereto.

Which was Filed application Continuity application (YYYY- Which is WhichSer. No. Type Ser. No. MM-DD) now issued on This claims 62/194,0542015-07-17 pending application benefit of This is a CIP of 14/676,7162015-04-01 pending — application 14/676,716 is a CNT of 14/203,4092014-03-10 pending — 14/203,409 is a CNT of 13/206,133 2011-08-09abandoned — 13/206,133 is a CNT of 12/479,638 2009-06-05 abandoned —12/479,638 is a DIV of 10/841,272 2004-05-07 abandoned — 10/841,272claims 60/468,741 2003-05-07 abandoned — benefit of 10/841,272 claims60/474,625 2003-05-29 abandoned — benefit of

FIELD OF THE INVENTION

The present invention relates generally to the field of fabricatingreentrant multi-layer three dimensional (e.g. micro-scale ormillimeter-scale) structures, parts, components, or devices where eachlayer is formed from a plurality of deposited materials and morespecifically where each layer is formed from at least one metalstructural material and at least one polymer-like sacrificial materialthat are co-planarized and at least a portion of the sacrificialmaterial located on a plurality of layers is removed after formation ofthe plurality of layers via one or more plasma or neutral radicaletching operations.

Background of the Invention

Electrochemical Fabrication:

An electrochemical fabrication technique for forming three-dimensionalstructures from a plurality of adhered layers is being commerciallypursued by Microfabrica® Inc. (formerly MEMGen Corporation) of Van Nuys,Calif. under the name Mica Freeform® (formerly EFAB®).

Various electrochemical fabrication techniques were described in U.S.Pat. No. 6,027,630, issued on Feb. 22, 2000 to Adam Cohen. Someembodiments of this electrochemical fabrication technique allow theselective deposition of a material using a mask that includes apatterned conformable material on a support structure that isindependent of the substrate onto which plating will occur. Whendesiring to perform an electrodeposition using the mask, the conformableportion of the mask is brought into contact with a substrate, but notadhered or bonded to the substrate, while in the presence of a platingsolution such that the contact of the conformable portion of the mask tothe substrate inhibits deposition at selected locations. Forconvenience, these masks might be generically called conformable contactmasks; the masking technique may be generically called a conformablecontact mask plating process. More specifically, in the terminology ofMicrofabrica Inc. such masks have come to be known as INSTANT MASKS™ andthe process known as INSTANT MASKING™ or INSTANT MASK™ plating.Selective depositions using conformable contact mask plating may be usedto form single selective deposits of material or may be used in aprocess to form multi-layer structures. The teachings of the '630 patentare hereby incorporated herein by reference as if set forth in fullherein. Since the filing of the patent application that led to the abovenoted patent, various papers about conformable contact mask plating(i.e. INSTANT MASKING) and electrochemical fabrication have beenpublished:

-   (1) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.    Will, “EFAB: Batch production of functional, fully-dense metal parts    with micro-scale features”, Proc. 9th Solid Freeform Fabrication,    The University of Texas at Austin, p 161, August 1998.-   (2) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.    Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High Aspect    Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro Mechanical    Systems Workshop, IEEE, p 244, January 1999.-   (3) A. Cohen, “3-D Micromachining by Electrochemical Fabrication”,    Micromachine Devices, March 1999.-   (4) G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P.    Will, “EFAB: Rapid Desktop Manufacturing of True 3-D    Microstructures”, Proc. 2nd International Conference on Integrated    MicroNanotechnology for Space Applications, The Aerospace Co., April    1999.-   (5) F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P.    Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal Microstructures    using a Low-Cost Automated Batch Process”, 3rd International    Workshop on High Aspect Ratio MicroStructure Technology (HARMST'99),    June 1999.-   (6) A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P.    Will, “EFAB: Low-Cost, Automated Electrochemical Batch Fabrication    of Arbitrary 3-D Microstructures”, Micromachining and    Microfabrication Process Technology, SPIE 1999 Symposium on    Micromachining and Microfabrication, September 1999.-   (7) F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P.    Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal Microstructures    using a Low-Cost Automated Batch Process”, MEMS Symposium, ASME 1999    International Mechanical Engineering Congress and Exposition,    November, 1999.-   (8) A. Cohen, “Electrochemical Fabrication (EFAB™)”, Chapter 19 of    The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC Press, 2002.-   (9) Microfabrication—Rapid Prototyping's Killer Application”, pages    1-5 of the Rapid Prototyping Report, CAD/CAM Publishing, Inc., June    1999.

The disclosures of these nine publications are hereby incorporatedherein by reference as if set forth in full herein.

An electrochemical deposition process for forming multilayer structuresmay be carried out in a number of different ways as set forth in theabove patent and publications. In one form, this process involves theexecution of three separate operations during the formation of eachlayer of the structure that is to be formed:

-   -   1. Selectively depositing at least one material by        electrodeposition upon one or more desired regions of a        substrate. Typically this material is either a structural        material or a sacrificial material.    -   2. Then, blanket depositing at least one additional material by        electrodeposition so that the additional deposit covers both the        regions that were previously selectively deposited onto, and the        regions of the substrate that did not receive any previously        applied selective depositions. Typically this material is the        other of a structural material or a sacrificial material.    -   3. Finally, planarizing the materials deposited during the first        and second operations to produce a smoothed surface of a first        layer of desired thickness having at least one region containing        the at least one material and at least one region containing at        least the one additional material.

After formation of the first layer, one or more additional layers may beformed adjacent to an immediately preceding layer and adhered to thesmoothed surface of that preceding layer. These additional layers areformed by repeating the first through third operations one or more timeswherein the formation of each subsequent layer treats the previouslyformed layers and the initial substrate as a new and thickeningsubstrate.

Once the formation of all layers has been completed, at least a portionof at least one of the materials deposited is generally removed by anetching process to expose or release the three-dimensional structurethat was intended to be formed. The removed material is a sacrificialmaterial while the material that forms part of the desired structure isa structural material.

One method of performing the selective electrodeposition involved in thefirst operation is by conformable contact mask plating. In this type ofplating, one or more conformable contact (CC) masks are first formed.The CC masks include a support structure onto which a patternedconformable dielectric material is adhered or formed. The conformablematerial for each mask is shaped in accordance with a particularcross-section of material to be plated (the pattern of conformablematerial is complementary to the pattern of material to be deposited).In such a process at least one CC mask is used for each uniquecross-sectional pattern that is to be plated.

The support for a CC mask may be a plate-like structure formed of ametal that is to be selectively electroplated and from which material tobe plated will be dissolved. In this typical approach, the support willact as an anode in an electroplating process. In an alternativeapproach, the support may instead be a porous or otherwise perforatedmaterial through which deposition material will pass during anelectroplating operation on its way from a distal anode to a depositionsurface. In either approach, it is possible for multiple CC masks toshare a common support, i.e. the patterns of conformable dielectricmaterial for plating multiple layers of material may be located indifferent areas of a single support structure. When a single supportstructure contains multiple plating patterns, the entire structure isreferred to as the CC mask while the individual plating masks may bereferred to as “submasks”. In the present application such a distinctionwill be made only when relevant to a specific point being made.

In some implementations, a single structure, part or device may beformed during execution of the above noted steps or in otherimplementations (batch processes) multiple identical or differentstructures, parts, or devices, may be built up simultaneously.

In preparation for performing the selective deposition of the firstoperation, the conformable portion of the CC mask is placed inregistration with and pressed against a selected portion of (1) thesubstrate, (2) a previously formed layer, or (3) a previously depositedmaterial forming a portion of the given layer that is being created. Thepressing together of the CC mask and relevant substrate, layer, ormaterial in such a way that all openings, in the conformable portions ofthe CC mask contain plating solution. The conformable material of the CCmask that contacts the substrate, layer, or material acts as a barrierto electrodeposition while the openings in the CC mask that are filledwith electroplating solution act as pathways for transferring materialfrom an anode (e.g. the CC mask support) to the non-contacted portionsof the substrate (which act as a cathode during the plating operation)when an appropriate potential and/or current are supplied.

An example of a CC mask and CC mask plating are shown in FIGS. 1A-10.FIG. 1A shows a side view of a CC mask 8 consisting of a conformable ordeformable (e.g. elastomeric) insulator 10 patterned on an anode 12. Theanode has two functions. One is as a supporting material for thepatterned insulator 10 to maintain its integrity and alignment since thepattern may be topologically complex (e.g., involving isolated “islands”of insulator material). The other function is as an anode for theelectroplating operation. FIG. 1A also depicts a substrate 6, separatedfrom mask 8, onto which material will be deposited during the process offorming a layer. CC mask plating selectively deposits material 22 ontosubstrate 6 by simply pressing the insulator against the substrate thenelectrodepositing material through apertures 26 a and 26 b in theinsulator as shown in FIG. 1B. After deposition, the CC mask isseparated, preferably non-destructively, from the substrate 6 as shownin FIG. 10.

The CC mask plating process is distinct from a “through-mask” platingprocess in that in a through-mask plating process the separation of themasking material from the substrate would occur destructively.Furthermore in a through mask plating process, opening in the maskingmaterial are typically formed while the masking material is in contactwith and adhered to the substrate. As with through-mask plating, CC maskplating deposits material selectively and simultaneously over the entirelayer. The plated region may consist of one or more isolated platingregions where these isolated plating regions may belong to a singlestructure that is being formed or may belong to multiple structures thatare being formed simultaneously. In CC mask plating as individual masksare not intentionally destroyed in the removal process, they may beusable in multiple plating operations.

Another example of a CC mask and CC mask plating is shown in FIGS.1D-1G. FIG. 1D shows an anode 12′ separated from a mask 8′ that includesa patterned conformable material 10′ and a support structure 20. FIG. 1Dalso depicts substrate 6 separated from the mask 8′. FIG. 1E illustratesthe mask 8′ being brought into contact with the substrate 6. FIG. 1Fillustrates the deposit 22′ that results from conducting a current fromthe anode 12′ to the substrate 6. FIG. 1G illustrates the deposit 22′ onsubstrate 6 after separation from mask 8′. In this example, anappropriate electrolyte is located between the substrate 6 and the anode12′ and a current of ions coming from one or both of the solution andthe anode are conducted through the opening in the mask to the substratewhere material is deposited. This type of mask may be referred to as ananodeless INSTANT MASK™ (AIM) or as an anodeless conformable contact(ACC) mask.

Unlike through-mask plating, CC mask plating allows CC masks to beformed completely separate from the substrate on which plating is tooccur (e.g. separate from a three-dimensional (3D) structure that isbeing formed). CC masks may be formed in a variety of ways, for example,using a photolithographic process. All masks can be generatedsimultaneously, e.g. prior to structure fabrication rather than duringit. This separation makes possible a simple, low-cost, automated,self-contained, and internally-clean “desktop factory” that can beinstalled almost anywhere to fabricate 3D structures, leaving anyrequired clean room processes, such as photolithography to be performedby service bureaus or the like.

An example of the electrochemical fabrication process discussed above isillustrated in FIGS. 2A-2F. These figures show that the process involvesdeposition of a first material 2 which is a sacrificial material and asecond material 4 which is a structural material. The CC mask 8, in thisexample, includes a patterned conformable material (e.g. an elastomericdielectric material) 10 and a support 12 which is made from depositionmaterial 2. The conformal portion of the CC mask is pressed againstsubstrate 6 with a plating solution 14 located within the openings 16 inthe conformable material 10. An electric current, from power supply 18,is then passed through the plating solution 14 via (a) support 12 whichdoubles as an anode and (b) substrate 6 which doubles as a cathode. FIG.2A illustrates that the passing of current causes material 2 within theplating solution and material 2 from the anode 12 to be selectivelytransferred to and plated on the substrate 6. After electroplating thefirst deposition material 2 onto the substrate 6 using CC mask 8, the CCmask 8 is removed as shown in FIG. 2B. FIG. 2C depicts the seconddeposition material 4 as having been blanket-deposited (i.e.non-selectively deposited) over the previously deposited firstdeposition material 2 as well as over the other portions of thesubstrate 6. The blanket deposition occurs by electroplating from ananode (not shown), composed of the second material, through anappropriate plating solution (not shown), and to the cathode/substrate6. The entire two-material layer is then planarized to achieve precisethickness and flatness as shown in FIG. 2D. After repetition of thisprocess for all layers, the multi-layer structure 20 formed of thesecond material 4 (i.e. structural material) is embedded in firstmaterial 2 (i.e. sacrificial material) as shown in FIG. 2E. The embeddedstructure is etched to yield the desired device, i.e. structure 20, asshown in FIG. 2F.

Various components of an exemplary manual electrochemical fabricationsystem 32 are shown in FIGS. 3A-3C. The system 32 consists of severalsubsystems 34, 36, 38, and 40. The substrate holding subsystem 34 isdepicted in the upper portions of each of FIGS. 3A-3C and includesseveral components: (1) a carrier 48, (2) a metal substrate 6 onto whichthe layers are deposited, and (3) a linear slide 42 capable of movingthe substrate 6 up and down relative to the carrier 48 in response todrive force from actuator 44. Subsystem 34 also includes an indicator 46for measuring differences in vertical position of the substrate whichmay be used in setting or determining layer thicknesses and/ordeposition thicknesses. The subsystem 34 further includes feet 68 forcarrier 48 which can be precisely mounted on subsystem 36.

The CC mask subsystem 36 shown in the lower portion of FIG. 3A includesseveral components: (1) a CC mask 8 that is actually made up of a numberof CC masks (i.e. submasks) that share a common support/anode 12, (2)precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 on whichthe feet 68 of subsystem 34 can mount, and (5) a tank 58 for containingthe electrolyte 16. Subsystems 34 and 36 also include appropriateelectrical connections (not shown) for connecting to an appropriatepower source (not shown) for driving the CC masking process.

The blanket deposition subsystem 38 is shown in the lower portion ofFIG. 3B and includes several components: (1) an anode 62, (2) anelectrolyte tank 64 for holding plating solution 66, and (3) frame 74 onwhich feet 68 of subsystem 34 may sit. Subsystem 38 also includesappropriate electrical connections (not shown) for connecting the anodeto an appropriate power supply (not shown) for driving the blanketdeposition process.

The planarization subsystem 40 is shown in the lower portion of FIG. 3Cand includes a lapping plate 52 and associated motion and controlsystems (not shown) for planarizing the depositions.

In addition to teaching the use of CC masks for electrodepositionpurposes, the '630 patent also teaches that the CC masks may be placedagainst a substrate with the polarity of the voltage reversed andmaterial may thereby be selectively removed from the substrate. Itindicates that such removal processes can be used to selectively etch,engrave, and polish a substrate, e.g., a plaque.

The '630 patent further indicates that the electroplating methods andarticles disclosed therein allow fabrication of devices from thin layersof materials such as, e.g., metals, polymers, ceramics, andsemiconductor materials. It further indicates that although theelectroplating embodiments described therein have been described withrespect to the use of two metals, a variety of materials, e.g.,polymers, ceramics and semiconductor materials, and any number of metalscan be deposited either by the electroplating methods therein, or inseparate processes that occur throughout the electroplating method. Itindicates that a thin plating base can be deposited, e.g., bysputtering, over a deposit that is insufficiently conductive (e.g., aninsulating layer) so as to enable subsequent electroplating. It alsoindicates that multiple support materials (i.e. sacrificial materials)can be included in the electroplated element allowing selective removalof the support materials.

The '630 patent additionally teaches that the electroplating methodsdisclosed therein can be used to manufacture elements having complexmicrostructure and close tolerances between parts. An example is givenwith the aid of FIGS. 14A-14E of that patent. In the example, elementshaving parts that fit with close tolerances, e.g., having gaps betweenabout 1-5 um, including electroplating the parts of the device in anunassembled, preferably pre-aligned, state. In such embodiments, theindividual parts can be moved into operational relation with each otheror they can simply fall together. Once together the separate parts maybe retained by clips or the like.

Another method for forming microstructures from electroplated metals(i.e. using electrochemical fabrication techniques) is taught in U.S.Pat. No. 5,190,637 to Henry Guckel, entitled “Formation ofMicrostructures by Multiple Level Deep X-ray Lithography withSacrificial Metal layers”. This patent teaches the formation of metalstructure utilizing through mask exposures. A first layer of a primarymetal is electroplated onto an exposed plating base to fill a void in aphotoresist (the photoresist forming a through mask having a desiredpattern of openings), the photoresist is then removed and a secondarymetal is electroplated over the first layer and over the plating base.The exposed surface of the secondary metal is then machined down to aheight which exposes the first metal to produce a flat uniform surfaceextending across both the primary and secondary metals. Formation of asecond layer may then begin by applying a photoresist over the firstlayer and patterning it (i.e. to form a second through mask) and thenrepeating the process that was used to produce the first layer toproduce a second layer of desired configuration. The process is repeateduntil the entire structure is formed and the secondary metal is removedby etching. The photoresist is formed over the plating base or previouslayer by casting and patterning of the photoresist (i.e. voids formed inthe photoresist) are formed by exposure of the photoresist through apatterned mask via X-rays or UV radiation and development of the exposedor unexposed areas.

The '637 patent teaches the locating of a plating base onto a substratein preparation for electroplating materials onto the substrate. Theplating base is indicated as typically involving the use of a sputteredfilm of an adhesive metal, such as chromium or titanium, and then asputtered film of the metal that is to be plated. It is also taught thatthe plating base may be applied over an initial layer of sacrificialmaterial (i.e. a layer or coating of a single material) on the substrateso that the structure and substrate may be detached if desired. In suchcases after formation of the structure the sacrificial material formingpart of each layer of the structure may be removed along with theinitial sacrificial layer to free the structure. Substrate materialsmentioned in the '637 patent include silicon, glass, metals, and siliconwith protected semiconductor devices. A specific example of a platingbase includes about 150 angstroms of titanium and about 300 angstroms ofnickel, both of which are sputtered at a temperature of 160° C. Inanother example it is indicated that the plating base may consist of 150angstroms of titanium and 150 angstroms of nickel where both are appliedby sputtering.

A need exists in various fields for miniature devices having improvedcharacteristics, reduced fabrication times, reduced fabrication costs,simplified fabrication processes, greater versatility in device design,improved selection of materials, improved material properties, more costeffective and less risky production of such devices, and/or moreindependence between geometric configuration and the selectedfabrication process.

Summary of the Invention

It is an object of some embodiments of the invention to provide animproved method for forming reentrant multi-layer three-dimensionalstructures from a plurality of adhered multi-material layers using atleast one polymer material as a sacrificial material and removing thepolymer material using plasma etching from a plurality of the layers(e.g. photoresists) wherein the sacrificial polymer (e.g. photoresists)becomes part of a plurality of multi-material layers and is removed froma group of the layers after formation of the group.

Other objects and advantages of various embodiments of the inventionwill be apparent to those of skill in the art upon review of theteachings herein. The various embodiments of the invention, set forthexplicitly herein or otherwise ascertained from the teachings herein,may address the above object or alternatively may address some otherobject ascertained from the teachings herein. It is not necessarilyintended that all objects be addressed by any single aspect of theinvention even though that may be the case with regard to some aspects.

In a first aspect of the invention a batch method for forming aplurality of three-dimensional structures, includes: (A) forming aplurality of successively formed multi-material layers, wherein eachsuccessive multi-material layer comprises at least two materials and isformed on and adhered to a previously formed multi-material layer, oneof the at least two materials is a structural material and the other ofthe at least two materials is a sacrificial material, and wherein eachsuccessive multi-material layer defines a successive cross-section ofthe plurality of three-dimensional structures, and wherein the formingof each of the plurality of successive multi-material layers includes:(i) depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; (iii) planarizing the first andsecond materials to set a boundary level for the multi-material layer;and wherein the forming of a given one or more of the plurality ofsuccessively formed multi-material layers includes: (i) applying a firstpatternable mold material (PMM) of portion of which will formed asacrificial material portion of the multi-material layer; (ii)patterning the first PMM to form a first pattern of sacrificialmaterial; (iii) depositing a structural material in openings in thefirst pattern of sacrificial material; (iv) planarizing the sacrificialmaterial and the structural material to set a boundary level for thegiven multi-material layer; and (B) after the forming of the pluralityof successive multi-material layers, separating at least a portion ofthe sacrificial material from multiple multi-material layers of thestructural material via plasma etching.

Numerous variations of the first aspect of the invention are possibleand include for example: (1) the PMM being a polymer; (2) the PMM beinga photoresist; (3) the PMM being a dielectric; (4) the PMM being aconductive epoxy; (5) the PMM being coated, at least in part, with aconductive material prior to depositing the structural material for thegiven one or more multi-material layer; (6) the 5^(th) variation whereinthe conductive material includes a seed layer; (7) the 6^(th) variationwherein the conductive material includes an adhesion layer; (8) the1^(st) aspect and any of the 1^(st)-7^(th) variations wherein afterformation of a selected multi-material layer but prior to the completionof the formation of all multi-material layers at least one intermediaterelease operation is performed to release at least selected regions ofthe sacrificial material from multiple multi-material layers includingat least one reentrant region existing under the selected layer andthereafter depositing a second sacrificial material and thereafterforming at least one additional multi-material layer above the selectedlayer and the second sacrificial material; (9) the 1^(st) aspect and anyof the 1^(st)-8^(th) variations wherein the second sacrificial materialdoes not fill all reentrant features where the first sacrificialmaterial was removed (10) either of the 8^(th) or 9^(th) variationwherein the second sacrificial material is easier to remove than thefirst sacrificial material by the plasma etching; (11) either of the9^(th) to 10^(th) variations wherein the structural material of theselected layer provides a feature selected from the group consisting of(a) a reentrant feature with an R-factor greater than 5, (b) a reentrantfeature with a R-factor greater than 10, (c) a reentrant feature with aR-factor greater than 20, and (d) a reentrant feature with a R-factorgreater than 50; (12) any of the 8^(th)-11^(th) variations wherein amulti-material layer above the selected layer contains structuralmaterial that provides a feature selected from the group consisting of(a) a reentrant feature with an R-factor greater than 5, (b) a reentrantfeature with a R-factor greater than 10, (c) a reentrant feature with aR-factor greater than 20, and (d) a reentrant feature with a R-factorgreater than 50; (13) the 1^(st) aspect and any of the 1^(st)-12^(th)variations wherein the structure includes one or more reentrant featureshaving an R-factor selected from the group consisting of (1) greaterthan 5, (2) greater than 10, (3) greater than 20, and (4) greater than50; (14) the plasma etching substantially is limited to etching withradicals; (15) the 14^(th) variation wherein the radicals includeradicals from O₂; (16) the 14th variation wherein the radicals areproduced from CF₄; (17) the 14^(th) variation wherein the radicals areproduced from NF₃; (18) the 1^(st) aspect and any of the 1^(st)-17^(th)variations wherein the etching occurs in a sub-atmospheric pressurechamber; (19) the 1^(st) aspect and any of the 1^(st)-18^(th) variationswherein one or more additional cleaning steps are performed after theplasma etching; (20) the 1^(st) aspect and any of the 1^(st)-19^(th)variations wherein the structural material includes at least one metal;(21) the 20^(th) variation wherein the structural material comprises atleast two different metals; (22) the 1^(st) aspect and any of the1st-21^(st) variations wherein the two different metals are deposited ontwo different multi-material layers; (23) the 21^(st) variation whereinthe two different metals are deposited as part of the samemulti-material layer; (24) the 1^(st) aspect and any of the1^(st)-23^(th) variations wherein the sacrificial material on at least aportion of the plurality of multi-material layers comprises SU-8:

(25) the 1^(st) aspect and any of the 1^(st)-24^(th) variations whereinformation of a particular multi-material layer includes the formation ofa non-planar seed layer when structural material forming part of theparticular multi-material layer overlays material other than metalstructural material on an immediately preceding multi-material layer;(26) the 1^(st) aspect and any of the 1^(st)-24^(th) variations whereinmulti-material layer formation comprises the formation of a planar seedlayer when structural material forming part of the particularmulti-material layer overlays material other than metal structuralmaterial on an immediately preceding multi-material layer; (27) the1^(st) aspect and any of the 1^(st)-24^(th) variations wherein plasmaetching comprises at least two etching operations which are separated byat least one non-plasma etching operation; (28) the 1^(st) aspect andany of the 1^(st) to 26^(th) variations wherein the removing includes anon-plasma etching operation as well as the plasma etching; (29) the1^(st) aspect and any of the 1^(st) to 28^(th) variations wherein atleast one of the depositing steps comprises electroplating; (30) the29^(th) variation wherein the depositing of the structural materialcomprises electroplating; (31) the 1^(st) aspect and any of the 1^(st)to 30^(th) variations wherein the given one or more multi-materiallayers comprise a number of multi-material layers selected from thegroup consisting of: (a) at least two multi-material layers; (b) atleast three multi-material layers; (c) a plurality of multi-materiallayers but less than all multi-material layers, (d) at least one half ofthe multi-material layers, (e) at least two thirds of the multi-materiallayers; and (f) all of the multi-material layers; (32) the 1^(st) aspectand any of the 1^(st) to 31^(st) variations wherein the structures areselected from the group consisting of (a) horizontally or verticallycomplex multilayer three-dimensional structures, (b) horizontally orvertically moderately complex multilayer three-dimensional structures,(c) horizontally or vertically highly complex multilayerthree-dimensional structures, (d) Reentrant multi-layerthree-dimensional structures, and (e) R-Factor extended reentrantmulti-layer three-dimensional structures with R factors greater thantwo.

In a second aspect of the invention a method for the batch formation ofa plurality of multi-layer structures, includes: (a) successivelyforming a plurality of multi-material layers, wherein each successivemulti-material layer is formed on an adhered to a precedingmulti-material layer, and wherein each of the plurality ofmulti-material layers comprises both a structural material and asacrificial material; and (b) after forming the plurality of adheredmulti-material layers, removing the sacrificial material from theplurality of plurality of multi-material layers to leave a multi-layerstructure comprising the structural material, wherein the multi-layerstructure comprises at least one reentrant feature, and wherein thesacrificial material comprises an organic material that is removed atleast in part by plasma etching.

Numerous variations of the second aspect of the invention are possibleand include for example the variations set forth for the 1^(st) aspectof the invention, mutatis mutandis.

The disclosure of the present invention provides various embodiments forthe batch formation of multi-layer three-dimensional structures witheach successive layer comprising at least two materials, one of which isa metal structural material and the other of which is an organicsacrificial material (e.g. a polymer or a solidified photoresist), andwherein each successively stacked and adhered layer defines a successivecross-section of the three-dimensional structure, and wherein theforming of each of the plurality of successive layers includes: (i)depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; (iii) planarizing the depositedmaterials that form the layer to set a boundary level for the layer; and(B) after the forming of a plurality of successive layers, separating atleast a portion of the sacrificial material, comprising an organicmaterial, e.g. a polymer or solidified photoresist, from the structuralmaterial to reveal the three-dimensional structure, wherein theimprovement includes: etching the sacrificial organic material from themetal structural material using a plasma etching process.

Other aspects of the invention will be understood by those of skill inthe art upon review of the teachings herein. Other aspects of theinvention may involve apparatus that can be used in implementing one ormore of the above method aspects of the invention. These other aspectsof the invention may provide various combinations of the aspectspresented above as well as provide other configurations, structures,functional relationships, and processes that have not been specificallyset forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C schematically depict side views of various stages of a CCmask plating process, while FIGS. 1D-1G schematically depict a sideviews of various stages of a CC mask plating process using a differenttype of CC mask.

FIGS. 2A-2F schematically depict side views of various stages of anelectrochemical fabrication process as applied to the formation of aparticular structure where a sacrificial material is selectivelydeposited while a structural material is blanket deposited.

FIGS. 3A-3C schematically depict side views of various examplesubassemblies that may be used in manually implementing theelectrochemical fabrication method depicted in FIGS. 2A-2F.

FIGS. 4A-4F schematically depict the formation of a first layer of astructure using adhered mask plating where the blanket deposition of asecond material overlays both the openings between deposition locationsof a first material and the first material itself

FIG. 4G depicts the completion of formation of the first layer resultingfrom planarizing the deposited materials to a desired level.

FIGS. 4H and 4I respectively depict the state of the process afterformation of the multiple layers of the structure and after release ofthe structure from the sacrificial material.

FIGS. 5A-5G provide schematic side cut views of a sample structure atvarious stages of the process of the first embodiment where thestructure is being formed from multiple multi-material layers thatinclude a metal structural material, a dielectric sacrificial material(e.g. an organic material such as a photoresist or photopolymer, such asSU-8), and a non-planar seed layer underlying and coating the sidewallsof the structural material wherein the structure is formed directly ontoa substrate and stays adhered to the substrate even after release of thestructure from sacrificial material wherein the release occurs via aplasma etching operation after the formation of all multi-materiallayers.

FIGS. 6A-6D provide schematic side cut views of a plurality of samplestructures illustrating various stages of a process for forming aplurality of structures according to a second embodiment of theinvention wherein the structures are formed indirectly on a substratewith an intervening release layer and wherein all layers of thestructures are formed prior to releasing the structures from both asacrificial organic material via a plasma etching operation and from thesubstrate via a plasma etching operation, a wet chemical etchingoperation, or via some other operation or operations.

FIGS. 7A-7G provide schematic side cut views of a plurality of samplestructures illustrating various stages in the forming of a plurality ofstructures according to another embodiment of the invention whichincludes (1) the partial formation of the structures including formationof a plurality of multi-material layers, (2) an initial release of thepartially formed structures from sacrificial material including removalof sacrificial material from undercut or reentrant regions, (3) partialback filling with the same or a different sacrificial material such thatsome voids remain in the most difficult to access undercut regions, (4)optionally planarizing to set a final boundary level for the last formedmulti-material layer, (5) forming the remaining multi-material layers ofthe structure, and (6) performing a final release of the structuralmaterial from multiple layers of sacrificial material and from thesubstrate wherein the final release is accomplished more readily, orwith less damage to the structure, due at least in part to the initialrelease that occurred.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Electrochemical Fabrication in General

FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of one form ofelectrochemical fabrication. Other electrochemical fabricationtechniques are set forth in the '630 patent referenced above, in thevarious previously incorporated publications, in various other patentsand patent applications incorporated herein by reference. Still othersmay be derived from combinations of various approaches described inthese publications, patents, and applications, or are otherwise known orascertainable by those of skill in the art from the teachings set forthherein. All of these techniques may be combined with those of thevarious other embodiments or various aspects of the invention to yieldenhanced embodiments. Still other embodiments may be derived from mixingand matching element and steps into new of combinations based on thevarious embodiments explicitly set forth herein.

FIGS. 4A-4I illustrate sides views of various states in an alternativemulti-layer, multi-material electrochemical fabrication process. FIGS.4A-4G illustrate various stages in the formation of a single layer of amulti-layer fabrication process where a second metal is deposited on afirst metal as well as in openings in the first metal so that the firstand second metal form part of the layer. In FIG. 4A a side view of asubstrate 82 having a surface 88 is shown, onto which patternablephotoresist 84 is cast as shown in FIG. 4B. In FIG. 4C, a pattern ofresist is shown that results from the curing, exposing, and developingof the resist. The patterning of the photoresist 84 results in openingsor apertures 92(a)-92(c) extending from a surface 86 of the photoresistthrough the thickness of the photoresist to surface 88 of the substrate82. In FIG. 4D a metal 94 (e.g. nickel) is shown as having beenelectroplated into the openings 92(a)-92(c). In FIG. 4E the photoresisthas been removed (i.e. chemically stripped) from the substrate to exposeregions of the substrate 82 which are not covered with the first metal94. In FIG. 4F a second metal 96 (e.g. silver) is shown as having beenblanket electroplated over the entire exposed portions of the substrate82 (which is conductive) and over the first metal 94 (which is alsoconductive). FIG. 4G depicts the completed first layer of the structurewhich has resulted from the planarization of the first and second metalsdown to a height that exposes the first metal and sets a thickness forthe first layer. In FIG. 4H the result of repeating the process stepsshown in FIGS. 4B-4G several times to form a multi-layer structure areshown where each layer consists of two materials. For most applications,one of these materials is removed as shown in FIG. 4I to yield a desired3-D structure 98 (e.g. component or device).

Various embodiments of various aspects of the invention are directed toformation of three-dimensional structures from materials some, or all,of which may be electrodeposited (as illustrated in FIGS. 1A-4I) orelectroless deposited. Some of these structures may be formed from asingle build level formed from one or more deposited materials whileothers are formed from a plurality of build layers each including atleast two materials (e.g. two or more layers, more preferably five ormore layers, and most preferably ten or more layers). In someembodiments micro-scale structures may be formed wherein layerthicknesses may be as small as one micron (1 um) or as large as fiftymicrons (50 um). In other embodiments, thinner layers may be used whilein other embodiments, thicker layers may be used. In some embodimentsmicro-scale structures may have features positioned with micron levelprecision (i.e. 0.1-5 microns) or smaller and minimum features size onthe order of microns to tens of microns (i.e. 5-50 microns). Suchmicro-scale structures may have dimensions that extend from a few tensof microns to tens of millimeters (e.g. 10 ums to 10 millimeters. Inother embodiments structures with less precise feature placement and/orlarger minimum features may be formed. In still other embodiments,higher precision and smaller minimum feature sizes may be desirable. Inthe present application meso-scale and millimeter scale have the samemeaning and refer to structures or devices that may have one or moredimensions extending into the 0.5-20 millimeter range, or somewhatlarger and with features positioned with precision in the 10-100 micronrange and with minimum features sizes on the order of 100-500 microns.

The various embodiments, alternatives, and techniques disclosed hereinmay form multi-layer structures using a single patterning technique onall layers or using different patterning techniques on different layers.For example, Various embodiments of the invention may perform selectivepatterning operations using conformable contact masks and maskingoperations (i.e. operations that use masks which are contacted to butnot adhered to a substrate), proximity masks and masking operations(i.e. operations that use masks that at least partially selectivelyshield a substrate by their proximity to the substrate even if contactis not made), non-conformable masks and masking operations (i.e. masksand operations based on masks whose contact surfaces are notsignificantly conformable), and/or adhered masks and masking operations(masks and operations that use masks that are adhered to a substrateonto which selective deposition or etching is to occur as opposed toonly being contacted to it). Conformable contact masks, proximity masks,and non-conformable contact masks share the property that they arepreformed and brought to, or in proximity to, a surface which is to betreated (i.e. the exposed portions of the surface are to be treated).These masks can generally be removed without damaging the mask or thesurface that received treatment to which they were contacted, or locatedin proximity to. Adhered masks are generally formed on the surface to betreated (i.e. the portion of that surface that is to be masked) andbonded to that surface such that they cannot be separated from thatsurface without being completely destroyed damaged beyond any point ofreuse. Adhered masks may be formed in a number of ways including (1) byapplication of a photoresist, selective exposure of the photoresist, andthen development of the photoresist, (2) selective transfer ofpre-patterned masking material, and/or (3) direct formation of masksfrom computer controlled depositions of material.

Patterning operations may be used in selectively depositing materialand/or may be used in the selective etching of material. Selectivelyetched regions may be selectively filled in or filled in via blanketdeposition, or the like, with a different desired material. In someembodiments, the layer-by-layer build up may involve the simultaneousformation of portions of multiple layers. In some embodiments,depositions made in association with some layer levels may result indepositions to regions associated with other layer levels (i.e. regionsthat lie within the top and bottom boundary levels that define adifferent layer's geometric configuration). Such use of selectiveetching and interlaced material deposition in association with multiplelayers is described in U.S. patent application Ser. No. 10/434,519, bySmalley, now U.S. Pat. No. 7,252,861, and entitled “Methods of andApparatus for Electrochemically Fabricating Structures Via InterlacedLayers or Via Selective Etching and Filling of Voids” which is herebyincorporated herein by reference as if set forth in full.

Temporary substrates on which structures may be formed may be of thesacrificial-type (i.e. destroyed or damaged during separation ofdeposited materials to the extent they cannot be reused),non-sacrificial-type (i.e. not destroyed or excessively damaged, i.e.not damaged to the extent they may not be reused, e.g. with asacrificial or release layer located between the substrate and theinitial layers of a structure that is formed). Non-sacrificialsubstrates may be considered reusable, with little or no rework (e.g.replanarizing one or more selected surfaces or applying a release layer,and the like) though they may or may not be reused for a variety ofreasons.

In still other embodiments other methods may be used to create andpattern layers. Such alternative techniques may for example involve theuse of sheets of material that are applied to previously formed layerswherein the sheets are patterned after deposition by selective etching,wet or dry, laser cutting or ablation, EDM processes, or the like. Inother alternative embodiments, deposits of structural or sacrificialmaterials may be patterned using similar methods.

In some embodiments, structures, multi-component devices or assembliesmay be built one at a time while in other embodiments (e.g. batchembodiments) multiple identical or dissimilar structures or devices maybe formed simultaneously (e.g. tens of structures, hundreds ofstructures, thousands, or even tens of thousands of structures).Structures may be formed on substrates such as round substrates that aresmaller than one inch in diameter to larger than eight or even twelveinches or more in diameter.

Definitions

This section of the specification is intended to set forth definitionsfor a number of specific terms that may be useful in describing thesubject matter of the various embodiments of the invention. It isbelieved that the meanings of most if not all of these terms is clearfrom their general use in the specification but they are set forthhereinafter to remove any ambiguity that may exist. It is intended thatthese definitions be used in understanding the scope and limits of anyclaims that use these specific terms. As far as interpretation of theclaims of this patent disclosure are concerned, it is intended thatthese definitions take presence over any contradictory definitions orallusions found in any materials which are incorporated herein byreference. Alternatives expressed in the following definitions may beused in creating various alternative embodiments of the invention and itis intended that all combinations of such alternatives be considered ascontemplated and taught herein.

“Build” as used herein refers, as a verb, to the process of building adesired structure (or part) plurality of structures (or parts) from aplurality of applied or deposited materials which are stacked andadhered upon application or deposition or, as a noun, to the physicalstructure (or part) or structures (or parts) formed from such a process.Depending on the context in which the term is used, such physicalstructures may include a desired structure embedded within a sacrificialmaterial or may include only desired physical structures which may beseparated from one another or may require dicing and/or slicing to causeseparation.

“Build axis” or “build orientation” is the axis or orientation that issubstantially perpendicular to substantially planar levels of depositedor applied materials that are used in building up a structure. Theplanar levels of deposited or applied materials may be or may not becompletely planar but are substantially so in that the overall extent oftheir cross-sectional dimensions are significantly greater than theheight of any individual deposit or application of material (e.g. 100,500, 1000, 5000, or more times greater). The planar nature of thedeposited or applied materials may come about from use of a process thatleads to planar deposits or it may result from a planarization process(e.g. a process that includes mechanical abrasion, e.g. lapping, flycutting, grinding, or the like) that is used to remove material regionsof excess height. Unless explicitly noted otherwise, “vertical” as usedherein refers to the build axis or nominal build axis (if the layers arenot stacking with perfect registration) while “horizontal” or “lateral”refers to a direction within the plane of the layers (i.e. the planethat is substantially perpendicular to the build axis).

“Build layer” or “layer of structure” as used herein does not refer to adeposit of a specific material but instead refers to a region of a buildlocated between a lower boundary level and an upper boundary level whichgenerally defines a single cross-section of a structure being formed orstructures which are being formed in parallel. Depending on the detailsof the actual process used to form the structure, build layers aregenerally formed on and adhered to previously formed build layers. Insome processes the boundaries between build layers are defined byplanarization operations which result in successive build layers beingformed on substantially planar upper surfaces of previously formed buildlayers. In some embodiments, the substantially planar upper surface ofthe preceding build layer may be textured to improve adhesion betweenthe layers. In other build processes, openings may exist in or be formedin the upper surface of a previous but only partially formed buildlayers such that the openings in the previous build layers are filledwith materials deposited in association with current build layers whichwill cause interlacing of build layers and material deposits. Suchinterlacing is described in U.S. patent application Ser. No. 10/434,519now U.S. Pat. No. 7,252,861. This referenced application is incorporatedherein by reference as if set forth in full. In most embodiments, abuild layer includes at least one primary structural material and atleast one primary sacrificial material. However, in some embodiments,two or more primary structural materials may be used without a primarysacrificial material (e.g. when one primary structural material is adielectric and the other is a conductive material). In some embodiments,build layers are distinguishable from each other by the source of thedata that is used to yield patterns of the deposits, applications,and/or etchings of material that form the respective build layers. Forexample, data descriptive of a structure to be formed which is derivedfrom data extracted from different vertical levels of a datarepresentation of the structure define different build layers of thestructure. The vertical separation of successive pairs of suchdescriptive data may define the thickness of build layers associatedwith the data. As used herein, at times, “build layer” may be looselyreferred simply as “layer”. In many embodiments, deposition thickness ofprimary structural or sacrificial materials (i.e. the thickness of anyparticular material after it is deposited) is generally greater than thelayer thickness and a net deposit thickness is set via one or moreplanarization processes which may include, for example, mechanicalabrasion (e.g. lapping, fly cutting, polishing, and the like) and/orchemical etching (e.g. using selective or non-selective etchants). Thelower boundary and upper boundary for a build layer may be set anddefined in different ways. From a design point of view they may be setbased on a desired vertical resolution of the structure (which may varywith height). From a data manipulation point of view, the vertical layerboundaries may be defined as the vertical levels at which datadescriptive of the structure is processed or the layer thickness may bedefined as the height separating successive levels of cross-sectionaldata that dictate how the structure will be formed. From a fabricationpoint of view, depending on the exact fabrication process used, theupper and lower layer boundaries may be defined in a variety ofdifferent ways. For example, they may be defined by planarization levelsor effective planarization levels (e.g. lapping levels, fly cuttinglevels, chemical mechanical polishing levels, mechanical polishinglevels, vertical positions of structural and/or sacrificial materialsafter relatively uniform etch back following a mechanical or chemicalmechanical planarization process). As another example, they may bedefined by levels at which process steps or operations are repeated. Asstill a further example, they may defined, at least theoretically, asthe vertical levels at which lateral extents of structural materials arechanged to define new cross-sectional features of a structure.

“Multi-material layer” as used herein refers to a build layer thatincludes multiple materials which typically includes at least onesacrificial material and at least one structural material located indifferent lateral region of the layer. Sometimes as used herein amulti-material layer may be referred to simply as a layer or a buildlayer (e.g. see the last word of the last sentence) and from the contextit will generally be clear as to what type of layer is being referred.In cases where the absolute clarity is not possible from the contextthen all possibilities are to be considered as explicitly set forth asindependent options though some may have less utility or relevance.

“Layer thickness” is the height along the build axis between a lowerboundary of a build layer and an upper boundary of that build layer.

“Planarization” is a process that tends to remove materials, above adesired plane, in a substantially non-selective manner such that alldeposited materials are brought to a substantially common height ordesired level (e.g. within 20%, 10%, 5%, or even 1% of a desired layerheight or boundary level). For example, lapping removes material in asubstantially non-selective manner though some amount of recession ofone material or another may occur (e.g. copper may recess relative tonickel). Planarization may occur primarily via mechanical means, e.g.lapping, grinding, fly cutting, milling, sanding, abrasive polishing,frictionally induced melting, other machining operations, or the like(i.e. mechanical planarization). Mechanical planarization may befollowed or preceded by thermally induced planarization (e.g. melting)or chemically induced planarization (e.g. etching). Planarization mayoccur primarily via a chemical and/or electrical means (e.g. chemicaletching, electrochemical etching, or the like). Planarization may occurvia a simultaneous combination of mechanical and chemical etching (e.g.chemical mechanical polishing (CMP)).

“Structural material” as used herein refers to a material that remainspart of the structure when put into use.

“Supplemental structural material” as used herein refers to a materialthat forms part of the structure when the structure is put to use but isnot added as part of the build layers but instead is added to aplurality of layers simultaneously (e.g. via one or more coatingoperations that applies the material, selectively or in a blanketfashion, to a one or more surfaces of a desired build structure that hasbeen released from a sacrificial material.

“Primary structural material” as used herein is a structural materialthat forms part of a given build layer and which is typically depositedor applied during the formation of that build layer and which makes upmore than 20% of the structural material volume of the given buildlayer. In some embodiments, the primary structural material may be thesame on each of a plurality of build layers or it may be different ondifferent build layers. In some embodiments, a given primary structuralmaterial may be formed from two or more materials by the alloying ordiffusion of two or more materials to form a single material. Thestructural material on a given layer may be a single primary structuralmaterial or may be multiple primary structural materials and may furtherinclude one or more secondary structural materials.

“Secondary structural material” as used herein is a structural materialthat forms part of a given build layer and is typically deposited orapplied during the formation of the given build layer but is not aprimary structural material as it individually accounts for only a smallvolume of the structural material associated with the given layer. Asecondary structural material will account for less than 20% of thevolume of the structural material associated with the given layer. Insome preferred embodiments, each secondary structural material mayaccount for less than 10%, 5%, or even 2% of the volume of thestructural material associated with the given layer. Examples ofsecondary structural materials may include seed layer materials,adhesion layer materials, barrier layer materials (e.g. diffusionbarrier material), and the like. These secondary structural materialsare typically applied to form coatings having thicknesses less than 2microns, 1 micron, 0.5 microns, or even 0.2 microns). The coatings maybe applied in a conformal or directional manner (e.g. via CVD, PVD,electroless deposition, or the like). Such coatings may be applied in ablanket manner or in a selective manner. Such coatings may be applied ina planar manner (e.g. over previously planarized layers of material) astaught in U.S. patent application Ser. No. 10/607,931, now U.S. Pat. No.7,239,219. In other embodiments, such coatings may be applied in anon-planar manner, for example, in openings in and over a patternedmasking material that has been applied to previously planarized layersof material as taught in U.S. patent application Ser. No. 10/841,383,now U.S. Pat. No. 7,195,989. These referenced applications areincorporated herein by reference as if set forth in full herein.

“Functional structural material” as used herein is a structural materialthat would have been removed as a sacrificial material but for itsactual or effective encapsulation by other structural materials.Effective encapsulation refers, for example, to the inability of anetchant to attack the functional structural material due toinaccessibility that results from a very small area of exposure and/ordue to an elongated or tortuous exposure path. For example, large(10,000 μm²) but thin (e.g. less than 0.5 microns) regions ofsacrificial copper sandwiched between deposits of nickel may defineregions of functional structural material depending on ability of arelease etchant to remove the sandwiched copper.

“Sacrificial material” is material that forms part of a build layer butis not a structural material. Sacrificial material on a given buildlayer is separated from structural material on that build layer afterformation of that build layer is completed and more generally is removedfrom a plurality of layers after completion of the formation of theplurality of layers during a “release” process that removes the bulk ofthe sacrificial material or materials. In general sacrificial materialis located on a build layer during the formation of one, two, or moresubsequent build layers and is thereafter removed in a manner that doesnot lead to a planarized surface. Materials that are applied primarilyfor masking purposes, i.e. to allow subsequent selective deposition oretching of a material, e.g. photoresist that is used in forming a buildlayer but does not form part of the build layer) or that exist as partof a build for less than one or two complete build layer formationcycles are not considered sacrificial materials as the term is usedherein but instead shall be referred as masking materials or astemporary materials. Photoresists that may be used to allow patterneddeposition of one or more subsequently applied materials and that stayin place during the formation of at least two layers (and morepreferably at least three layers) may be considered sacrificialmaterials (e.g. unless excluded by more restrictive limitations,photoresists or other photo patternable materials that stay in placeduring formation of a given layer and thereafter such that material of asubsequent layer is formed thereon may be considered a sacrificialmaterial). Such photoresists or other polymers that are consideredsacrificial materials will generally undergo layer-by-layerplanarization along with structural materials. Photoresists or otherpolymeric or organic materials that are deposited in a multi-layerfashion to occupy regions of a plurality of layers which initiallyincluded use of a different sacrificial material may be consideredsacrificial materials. These separation processes are sometimes referredto as a release process and may or may not involve the separation ofstructural material from a build substrate (e.g. via a release layer ofa sacrificial material). In many embodiments, sacrificial materialwithin a given build layer is not removed until all build layers makingup the three-dimensional structure have been formed. Of coursesacrificial material may be, and typically is, removed from above theupper level of a current build layer during planarization operationsduring the formation of the current build layer. During release orseparation, sacrificial material is typically removed via a chemicaletching operation (e.g. a wet isotropic chemical etching operation thatattacks exposed sacrificial material but not structural material to anyappreciable level. In some embodiments it may be removed via a meltingoperation, electrochemical etching operation, laser ablation, or thelike. In the present invention at least a portion of an organicsacrificial material (e.g. polymeric material, negative or positivephotoresist material) is removed via some form dry etching (e.g. plasmaetching via reaction of an organic or even some metallic materials witheither plasma or radicals that may have been initially created by aplasma, or by radical etching where the radicals are created byradiation exposure or other non-plasma based methods). In typicalstructures, the removal of the sacrificial material (i.e. release of thestructural material from the sacrificial material) does not result inplanarized surfaces but instead results in surfaces that are dictated bythe boundaries of structural materials located on each build layer.Sacrificial materials are typically distinct from structural materialsby having different properties therefrom (e.g. chemical etchability,hardness, melting point, etc.) but in some cases, as noted previously,what would have been a sacrificial material may become a structuralmaterial by its actual or effective encapsulation by other structuralmaterials. Similarly, structural materials may be used to formsacrificial structures that are separated from a desired structureduring a release process via the sacrificial structures being onlyattached to sacrificial material or potentially by dissolution of thesacrificial structures themselves using a process that is insufficientto reach structural material that is intended to form part of a desiredstructure. It should be understood that in some embodiments, smallamounts of structural material may be removed, after or during releaseof sacrificial material. Such small amounts of structural material mayhave been inadvertently formed due to imperfections in the fabricationprocess or may result from the proper application of the process but mayresult in features that are less than optimal and in some case featuresthat have been beneficially modified (e.g. layers with stair steps inregions where smooth sloped surfaces are desired). In such cases thevolume of structural material removed is typically minuscule compared tothe amount that is retained and thus such removal is ignored whenlabeling materials as sacrificial or structural. Sacrificial materialsare typically removed by a dissolution process, or the like, thatdestroys the geometric configuration of the sacrificial material as itexisted on the build layers. In many embodiments, the sacrificialmaterial is a conductive material, such as a metal, though in someembodiments it may be a dielectric material and even a photoresistmaterial. As will be discussed hereafter, masking materials thoughtypically sacrificial in nature are not termed sacrificial materialsherein unless they meet the required definition of sacrificial material.

“Supplemental sacrificial material” as used herein refers to a materialthat does not form part of the structure when the structure is put touse and is not added as part of the build layers but instead is added toa plurality of layers simultaneously (e.g. via one or more coatingoperations that applies the material, selectively or in a blanketfashion, to a one or more surfaces of a desired build structure that hasbeen released from an initial sacrificial material. This supplementalsacrificial material will remain in place for a period of time and/orduring the performance of certain post layer formation operations, e.g.to protect the structure that was released from a primary sacrificialmaterial, but will be removed prior to putting the structure to use.

“Primary sacrificial material” as used herein is a sacrificial materialthat is located on a given build layer and which is typically depositedor applied during the formation of that build layer and which makes upmore than 20% of the sacrificial material volume of the given buildlayer. In some embodiments, the primary sacrificial material may be thesame on each of a plurality of build layers or may be different ondifferent build layers. In some embodiments, a given primary sacrificialmaterial may be formed from two or more materials by the alloying ordiffusion of two or more materials to form a single material. Thesacrificial material on a given layer may be a single primarysacrificial material or may be multiple primary sacrificial materialsand may further include one or more secondary sacrificial materials.

“Secondary sacrificial material” as used herein is a sacrificialmaterial that is located on a given build layer and is typicallydeposited or applied during the formation of the build layer but is nota primary sacrificial material as it individually accounts for only asmall volume of the sacrificial material associated with the givenlayer. A secondary sacrificial material will account for less than 20%of the volume of the sacrificial material associated with the givenlayer. In some preferred embodiments, each secondary sacrificialmaterial may account for less than 10%, 5%, or even 2% of the volume ofthe sacrificial material associated with the given layer. Examples ofsecondary sacrificial materials may include seed layer materials,adhesion layer materials, barrier layer materials (e.g. diffusionbarrier material), and the like. These secondary sacrificial materialsare typically applied to form coatings having thicknesses less than 2microns, 1 micron, 0.5 microns, or even 0.2 microns or less). Thecoatings may be applied in a conformal or directional manner (e.g. viaCVD, PVD, electroless deposition, or the like). Such coatings may beapplied in a blanket manner or in a selective manner. Such coatings maybe applied in a planar manner (e.g. over previously planarized layers ofmaterial) as taught in U.S. patent application Ser. No. 10/607,931, nowU.S. Pat. No. 7,239,219. In other embodiments, such coatings may beapplied in a non-planar manner, for example, in openings in and over apatterned masking material that has been applied to previouslyplanarized layers of material as taught in U.S. patent application Ser.No. 10/841,383, now U.S. Pat. No. 7,195,989. These referencedapplications are incorporated herein by reference as if set forth infull herein.

“Adhesion layer”, “seed layer”, “barrier layer”, and the like refer tocoatings of material that are thin in comparison to the layer thicknessand thus generally form secondary structural material portions orsacrificial material portions of some layers. Such coatings may beapplied uniformly over a previously formed build layer, they may beapplied over a portion of a previously formed build layer and overpatterned structural or sacrificial material existing on a current (i.e.partially formed) build layer so that a non-planar seed layer results,or they may be selectively applied to only certain locations on apreviously formed build layer. In the event such coatings arenon-selectively applied, selected portions may be removed (1) prior todepositing either an additional sacrificial material or structuralmaterial as part of a current layer or (2) prior to beginning formationof the next layer or they may remain in place through the layer build upprocess and then be etched away after formation of a plurality of buildlayers (e.g. as either part of a single release process, part of amulti-step release process that alternately removes sacrificial materialand these adhesion, seed or barrier layer materials, or as part of someother multi-step release process.

“Masking material” is a material that may be used as a tool in theprocess of forming a build layer but does not generally form part ofthat build layer. Masking material is typically a photopolymer orphotoresist material (e.g. a photo-patternable material) or othermaterial that may be readily patterned. Masking material is typically adielectric. Masking material, though typically sacrificial in nature, isnot a sacrificial material as the term is used herein unless certainrequirements are met. Masking material is typically applied to a surfaceduring the formation of a build layer for the purpose of allowingselective deposition, etching, or other treatment and is removed eitherduring the process of forming that build layer or immediately after theformation of that build layer. In the embodiments herein, maskingmaterial or photo patternable material may or may not function as asacrificial material.

“Multilayer structures” are structures formed from multiple build layersof deposited or applied materials.

“Multilayer three-dimensional (or 3D or 3-D) structures” are multilayerstructures wherein the structural material portions of at least twosuccessive layers are not identical in configuration, not identical inlateral position, or not identical in orientation (i.e. the structuralmaterials on the two successive layers do not completely overlap onanother.

Reentrant multi-layer three-dimensional structures are multi-layerthree-dimensional structures where structural material of a subsequentlayer covers an area of sacrificial material of a previous layer. Inother words, a structural material on a subsequent layer that occupies alateral position different from that of structural material on aprevious layer, will form an up-facing feature from material on thepreceding layer that is not overlaid by structural material and/or willhave a down-facing feature on its underside, where there is noimmediately underlying structural material. Such a down-facing featurefor the purpose of this application defines a reentrant feature.

“R-Factor extended reentrant multi-layer three-dimensional structures”are reentrant multi-layer three-dimensional structures where structuralmaterial of a single subsequent layer, a selected portion of thesubsequent layer, or a plurality of subsequent layers or selectedportions thereof taken in combination, provide a structural materialcover over a region or volume of sacrificial material of a singleprevious layer, or of plurality of previous layers taken in combination,where the region may be defined to have and R-Factor defined byR-Factor=(THCA+HAA)/(HAA+VAA)

where

-   -   THCA=Total Horizontal Coverage Area=The horizontal area (having        a normal parallel to the build axis (e.g. Z-axis) is defined by        the union of areas of coverage provided by structural material        of one or more subsequent layers or layer portions that are to        be considered. In some implementations, a sum of down-facing        areas of the relevant structural material regions may be used to        define the THCA.    -   HAA=Horizontal Access Area=The effective area of horizontal        openings within the THCA    -   VAA=Vertical Access Area=The effective area of vertical openings        (having a normal perpendicular to the build axis) extending        downward from the structural material of the one or more        subsequent layers.        The effective areas noted above may be less than the actual        areas due to the presence of regions of structural material that        are not located on the horizontal surface or vertical surfaces        themselves but are located such that they can inhibit or reduce        etchant access. The larger the R-Factor the more difficult for        etchants (e.g. radicals from CF₄ and O₂) to access and remove        material from reentrant regions). R-factors may, for example,        range from 0 (i.e. no coverage) to 1 (coverage and access have        approximately equal extents), 2, 5, 10, 20, 50, 100, 200, 500 or        even more.

“Complex multilayer three-dimensional (or 3D or 3-D) structures” aremultilayer three-dimensional structures formed from at least threelayers where a line may be defined that hypothetically extendsvertically through at least some portion of the build layers of thestructure and that extends from structural material through sacrificialmaterial and back through structural material or extends fromsacrificial material through structural material and back throughsacrificial material (these might be termed vertically complexmultilayer three-dimensional structures). Alternatively, complexmultilayer three-dimensional structures may be defined as multilayerthree-dimensional structures formed from at least two layers where aline may be defined that hypothetically extends horizontally through atleast some portion of a build layer of the structure that will extendfrom structural material through sacrificial material and back throughstructural material or will extend from sacrificial material throughstructural material and back through sacrificial material (these mightbe termed horizontally complex multilayer three-dimensional structures).Worded another way, in complex multilayer three-dimensional structures,a vertically or horizontally extending hypothetical line will extendfrom one of structural material or void (when the sacrificial materialis removed) to the other of void or structural material and then back tostructural material or void as the line is traversed along its length.Complex multi-layer three-dimensional structures may be further definedas either vertically or horizontally complex when such distinction isimportant.

“Moderately complex multilayer three-dimensional (or 3D or 3-D)structures are complex multilayer 3D structures for which thealternating of void and structure or structure and void not only existsalong one of a vertically or horizontally extending line but along linesextending both vertically and horizontally. Highly complex multi-layerthree-dimensional structures may be further defined as either verticallyor horizontally highly complex when such distinction is important.

“Highly complex multilayer (or 3D or 3-D) structures are complexmultilayer 3D structures for which the structure-to-void-to-structure orvoid-to-structure-to-void alternating occurs not only once along theline but occurs a plurality of times along a definable horizontally orvertically extending line. Highly complex multi-layer three-dimensionalstructures may be further defined as either vertically or horizontallyhighly complex when such distinction is important.

“Up-facing feature” is an element dictated by the cross-sectional datafor a given build layer “n” and a next build layer “n+1” that is to beformed from a given material that exists on the build layer “n” but doesnot exist on the immediately succeeding build layer “n+1”. Forconvenience the term “up-facing feature” will apply to such featuresregardless of the build orientation.

“Down-facing feature” is an element dictated by the cross-sectional datafor a given build layer “n” and a preceding build layer “n−1” that is tobe formed from a given material that exists on build layer “n” but doesnot exist on the immediately preceding build layer “n−1”. As withup-facing features, the term “down-facing feature” shall apply to suchfeatures regardless of the actual build orientation.

“Continuing region” is the portion of a given build layer “n” that isdictated by the cross-sectional data for the given build layer “n”, anext build layer “n+1” and a preceding build layer “n−1” that is neitherup-facing nor down-facing for the build layer “n”.

“Minimum feature size” or “MFS” refers to a necessary or desirablespacing between structural material elements on a given layer that areto remain distinct in the final device configuration. If the minimumfeature size is not maintained for structural material elements on agiven layer, the fabrication process may result in structural materialinadvertently bridging what were intended to be two distinct elements(e.g. due to masking material failure or failure to appropriately fillvoids with sacrificial material during formation of the given layer suchthat during formation of a subsequent layer structural materialinadvertently fills the void). More care during fabrication can lead toa reduction in minimum feature size. Alternatively, a willingness toaccept greater losses in productivity (i.e. lower yields) can result ina decrease in the minimum feature size. However, during fabrication fora given set of process parameters, inspection diligence, and yield(successful level of production) a minimum design feature size is set inone way or another. The above described minimum feature size may moreappropriately be termed minimum feature size of gaps or voids (e.g. theMFS for sacrificial material regions when sacrificial material isdeposited first). Conversely a minimum feature size for structurematerial regions (minimum width or length of structural materialelements) may be specified. Depending on the fabrication method andorder of deposition of structural material and sacrificial material, thetwo types of minimum feature sizes may be the same or different. Inpractice, for example, using electrochemical fabrication methods asdescribed herein, the minimum features size on a given layer may beroughly set to a value that approximates the layer thickness used toform the layer and it may be considered the same for both structural andsacrificial material widths. In some more rigorously implementedprocesses (e.g. with higher examination regiments and tolerance forrework), it may be set to an amount that is 80%, 50%, or even 30% of thelayer thickness. Other values or methods of setting minimum featuresizes may be used. Worded another way, depending on the geometry of astructure, or plurality of structures, being formed, the structure, orstructures, may include elements (e.g. solid regions) which havedimensions smaller than a first minimum feature size and/or havespacings, voids, openings, or gaps (e.g. hollow or empty regions)located between elements, where the spacings are smaller than a secondminimum feature size where the first and second minimum feature sizesmay be the same or different and where the minimum feature sizesrepresent lower limits at which formation of elements and/or spacing canbe reliably formed. Reliable formation refers to the ability toaccurately form or produce a given geometry of an element, or of thespacing between elements, using a given formation process, with aminimum acceptable yield. The minimum acceptable yield may depend on anumber of factors including: (1) number of features present per layer,(2) numbers of layers, (3) the criticality of the successful formationof each feature, (4) the number and severity of other factors effectingoverall yield, and (5) the desired or required overall yield for thestructures or devices themselves. In some circumstances, the minimumsize may be determined by a yield requirement per feature which is aslow as 70%, 60%, or even 50%. While in other circumstances the yieldrequirement per feature may be as high as 90%, 95%, 99%, or even higher.In some circumstances (e.g. in producing a filter element) the failureto produce a certain number of desired features (e.g. 20-40% failure maybe acceptable while in an electrostatic actuator the failure to producea single small space between two moveable electrodes may result infailure of the entire device. The MFS, for example, may be defined asthe minimum width of a narrow and processing element (e.g. photoresistelement or sacrificial material element) or structural element (e.g.structural material element) that may be reliably formed (e.g. 90-99.9times out of 100) which is either independent of any wider structures orhas a substantial independent length (e.g. 200-1000 microns) beforeconnecting to a wider region.

Formation and Release Examples:

Multi-layer three-dimensional structures may be formed in a variety ofdifferent ways according to different embodiments of the invention.Examples of such embodiments and variations include the various methodsfor incorporating dielectrics and metals as taught in U.S. patentapplication Ser. Nos. 14/185,613; 11/478,934; 10/607,931; 14/203,409;and 11/478,934 which are hereby incorporated herein by reference. Othermethods may use the teachings of U.S. patent application Ser. No.14/154,119 regarding the formation of structures using HTED materials.Still other embodiments may use the multi-structural material methodsset forth in these applications as well as in the various additionalapplications that are incorporated herein by reference.

In a first embodiment, a multi-layer three-dimensional structure isformed from a plurality of adhered multi-material layers where oneconductive material is electrodeposited and where a masking material isan organic material and is used as sacrificial material. This embodimentincludes four steps that are repeated a plurality of times in formingthe multi-layer structure.

The primary operations of this embodiment include (1) forming a mask onthe substrate (e.g. an actual substrate, a release layer or barrierlayer on a substrate, or a previously formed multi-material layer if thepresent layer is not the first layer) by depositing and then patterningan organic material, such as photoresist, or by selectively dispensing amasking material from an ink jet device or by transfer plating or thelike to a height greater than or equal to the layer thickness of thepresent layer, (2) depositing a seed layer into the voids in the maskproduced from this organic material as well as onto the exposed uppersurface of the masking material (e.g. by sputtering and/or electrolessdeposition), (3) depositing a conductive first material to a heightequal to or greater than the layer thickness of the present layer (e.g.via an electrodeposition or possibly an electroless depositionoperation) into the voids in the masking material and potentially abovethe masking material, and (4) planarizing the deposited materials to theheight of the present layer to bound the present layer Thisplanarization trims off any excess thickness of the first material andany excess thickness of the mask material as well as the adhesion/seedlayer that is located above the masking material. Next, the processrepeats operations (1)-(4) one or more times to form a multi-layerstructure that includes two materials per layer one of which is the maskmaterial. The operations result in seed layer material only beinglocated in the boundary regions between the conductive first materialand the masking material on the present layer and along the layerboundary separating the conductive material between the present layerand any preceding layer. In this implementation, planarization is allthat is need to remove the adhesion/seed layer material from unwantedareas. Finally, after layer formation is complete, masking material isremoved by plasma etching (e.g. etching with neutral radicals producedby a plasma and then separated from the plasma and allowed to contactthe masking material and react with it so as to make primarily gaseousby products that can be removed by vacuum.

Numerous alternatives to the this first embodiment exist and include,for example: (1) eliminating step 2 on those layers where the depositedstructural material is deposited only on structural material existing onthe previous layer, (2) using the indicated four steps during theformation of some layers but using other steps during formation of otherlayers, (3) incorporation of additional deposition steps, etching steps,planarization steps (e.g. intermediate planarization operations thatplanarize to a height above a layer boundary level) to form structureswith additional structural or sacrificial materials on some layers, (4)performing some preliminary etching release operations prior tocompleting layer formation and possibly partially back filling into thevoids around the structural material or backfilling completely with amaterial having different properties, (5) adding additional releaseoperations such as wet etching, (6) adding in cleaning operations usingsolvents, gas flow, supercritical material flow, or the like, (7) use ofactivation operations to enhance bonding of deposited materials, (8)formation of single structures one at a time or batch fabrication of aplurality of identical or different structures, (9) formation ofstructures that have multiple components that may be moveable relativeto one another, (10) formation of structures that do not adhere directlyto a substrate but which are separated from the substrate by a releaselayer (which may actually be considered a part of the substrate and evena repairable part of the substrate if the substrate is to be reused) towhich the first layer of the structure adheres and which can be used torelease the structure from the substrate after formation, (11) of coursedifferent shaped structures may be formed, (12) structures may be formedwith different numbers of layers, different layer thicknesses, varyinglayer thicknesses, different materials on some or all layers, and thelike, (13) additional processing may be performed to reshape the stairsteps generally associated with layer-by-layer fabrication or to improveetching access to reentrant regions either via permanent access featuresthrough the structural material or via temporary access features thatare filled in with structural material during subsequent layer formationsuch as the processes or modifications taught in U.S. patent applicationSer. Nos. 10/607,931, 10/830,262, and 12/828,274 which are eachincorporated herein by reference.

FIGS. 5A-5G provide schematic side cut views of a sample structure(which may be one of many structures being simultaneously formed in abatch process) at various stages of the process of the first embodimentwhere the structure is being formed from multiple multi-material layersthat include a metal structural material, a dielectric sacrificialmaterial (e.g. an organic material such as a photoresist orphotopolymer, such as SU-8), and a non-planar seed layer underlying andcoating the sidewalls of the structural material wherein the structureis formed directly onto a substrate and stays adhered to the substrateeven after release of the structure from sacrificial material whereinthe release occurs via a plasma etching operation after the formation ofall multi-material layers.

FIG. 5A depicts a substrate 122. This substrate is provided to act as abase on to which successive multi-material layers of the structure willbe formed. In some embodiments the substrate may be, for example, ametal, a ceramic (conductive or non-conductive), a plastic, or asemiconductor material with or without active electronic componentsformed thereon.

FIG. 5B depicts a mask structure 124 adhered to substrate 122. The maskmay, for example, be formed by depositing a photoresist and then usinglithography and development to pattern it. In other alternatives themask may be formed by ink jetting or extruding a material in a desiredpattern or by transfer plating and then transforming that material intoa solid.

FIG. 5C depicts the state of the process after a seed layer 126 isformed above mask material 124 and substrate 122. The seed layer may bea single metal or it may be a combination of materials such as anadhesion promoter followed by a plating promotor both deposited, forexample, by sputtering. In other alternatives a barrier layer may beincluded to help prevent migration of a conductive structural materialto the substrate.

FIG. 5D depicts the state of the process after deposition of a firstconductive material 128 (i.e. a structural material) while FIG. 5Edepicts the state of the process after planarization of the depositedmaterials down to a layer thickness LT of the first multi-material layerL1.

FIG. 5F depicts the state of the process after formation of twoadditional multi-material layers L2 and L3, where each multi-materiallayer includes masking material 124, seed layer material 126, andconductive material 128. In this embodiment, the masking material 124not only functions as a masking material but as a sacrificial materialwhile the conductive material 128 functions as a structural material andmore particularly as a primary structural material. In some embodimentsthese materials may be the same from multi-material layer tomulti-material layer, in other embodiments they may differ on somemulti-material layers, in still others one or more may not exist on somemulti-material layers, while in still others additional materials mayexist on some or all multi-material layers.

FIG. 5G depicts the state of the process after removal of the maskingmaterial by exposure to a plasma etching material (e.g. radicals of O₂,CF₄, or NF₃) as indicated by elements 140 which, as noted above, is alsofunctioning as a sacrificial material and more particularly as adielectric sacrificial material. In some variations some of the maskingmaterial or other dielectric material may be retained as a structuralcomponent especially if it is encapsulated by structural material or hasa property, attribute, or feature that inhibits it from being removedwith the other material (e.g. difficult access path).

FIGS. 6A-6D provide schematic side cut views of a plurality of samplestructures at various stages of a process for forming a plurality ofstructures according to a second embodiment of the invention wherein thestructures are formed indirectly on a substrate with an interveningrelease layer (e.g. a single material layer formed from a material thatmay be separated from the structural material without damaging thestructural material such as, for example an organic sacrificial materialor a conductive structural material) and wherein all multi-materiallayers of the structures are formed prior to releasing the structuresfrom both a sacrificial organic material via a plasma etching operationand from the substrate via a plasma etching operation or via some otheroperation or operation (such as a wet chemical etching operation).

FIG. 6A shows the state of the process after formation of a releaselayer on a substrate and five multi-material layers on the release layerand on each other. The multi-material layers, in this example include ametal structural material and a polymeric sacrificial material that mayor may not have functioned as a patterning material.

FIG. 6B shows the state of the process after a plasma based releaseoperation or set of operations begins to remove the sacrificial materialwhile FIG. 6C shows the state of the process after most of thesacrificial material is removed. In both FIGS. 6B and 6C a portion ofthe sacrificial material remains. In FIG. 6B the remaining portionincludes both sacrificial material forming part of the multi-materiallayers and material of the release layer while FIG. 6B has only releasematerial remaining.

FIG. 6D shows the state of the process after all of the sacrificialmaterial (including material of the release layer) and substrate havebeen removed.

The embodiment illustrated in FIGS. 6A-6D may be modified in many waysincluding modifications that incorporate some of the features of thefirst embodiment or its variations. Likewise the first embodiment mayincorporate some of the features of this embodiment.

FIGS. 7A-7G provide schematic side cut views of a plurality of samplestructures illustrating various stages in the forming of a plurality ofstructures according to another embodiment of the invention whichincludes (1) the partial formation of the structures including formationof a plurality of multi-material layers, (2) an initial release of thepartially formed structures from sacrificial material including removalof sacrificial material from undercut or reentrant regions, (3) partialback filling with the same or a different sacrificial material such thatsome voids remain in the most difficult to access undercut regions, (4)optionally planarizing to set a final boundary level for the last formedmulti-material layer, (5) forming the remaining multi-material layers ofthe structure, and (6) performing a final release of the structuralmaterial from multiple layers of sacrificial material and from thesubstrate wherein the final release is accomplished more readily, orwith less damage to the structure, due at least in part to the initialrelease that occurred. In some alternative embodiments, the partial backfilling may be a complete back filling if the initial sacrificialmaterial is replaced with a more readily removable sacrificial material.

FIG. 7A depicts the state of the process similar to that noted in FIG.6A with the exception that only a portion of the required multi-materiallayers have been formed (e.g. multi-material layers 1-n of N) on asubstrate 701 which has a release layer LO of sacrificial material overwhich exists 5 multi-material layers with each have a structuralmaterial 700 and a sacrificial material 702. The portion of the layersthat have been formed provide, in this example, some undercut orreentrant features 706 and represent a geometry that still providesreasonable access to interior portions of the individual structures butwhich will experience a significant reduction in access after formationof a next layer. For either of these reasons, stopping layer formationat this point and doing some in situ sacrificial release can bebeneficial in terms of overall processing time or less damage tostructural material as less material removal will be required later or asimpler removal may be implemented later. In some alternatives thesignificant reduction in access may not occur after the formation of theimmediately succeeding layer but from a subsequent layer that is to beformed. In some alternative embodiments the sacrificial material of therelease layer may be different than the sacrificial material of themulti-material layers.

FIG. 7B depicts the state of the process after an etching operationwhich is depicted with arrows (which may be plasma etching operation orset of operations or some other form of release) has removed thesacrificial material (or at least a desired portion of it).

FIG. 7C depicts the state of the process after a back filling of asacrificial material 702-2 (which may or may not be different from theoriginal sacrificial material 702 that was used) to partially back fillthe reentrant features leaving the hardest to reach regions 716 free ofsacrificial material. In other alternative embodiments, sacrificialmaterial may refill all portions of the reentrant features but suchmaterial may be easier to remove than the original sacrificial material.

FIG. 7D depicts the state of the process after a planarization or atleast smoothing and possibly a cleaning operation prepare the uppersurface of the last formed multi-material layer for receiving one ormore additional layers. As shown the overlaying sacrificial material isremoved and the height of the structural material and the sacrificialmaterial are brought to a common level which matches the desiredboundary level of the last formed multi-material layer.

FIG. 7E depicts the state of the process after layer formation iscompleted while FIG. 7F depicts the state of the process after anotheretching operation or set of operations is partially performed while FIG.7G shows the state of the process after complete removal of thesacrificial material and release of the structures from both thesacrificial material and the substrate.

In the embodiment of FIGS. 7A-7G two release etching operations or twosets of etching operations are performed at least one of which is aplasma etching operation (e.g. removal of sacrificial material viareactive non-ionized radicals). In some implementations both sets wouldbe plasma etching operations.

As with the first and second embodiments, numerous variations of thethird embodiment are possible and include the variations and features ofthe first and second embodiments but further include the possibility ofperforming more than one intermediate etching processes and particularlyafter or before forming layers that provide significant transitions,such as reentrant features with large R-values or where an upcominglayer would provide a significant reduction in etching access. Otherpossibilities include using shielding or other etching inhibitiontechniques to limit regions of etching. In some embodiments, even thelast etching operation may use shields or the like to allow selectiverelease of structures.

In some embodiments, plasma etching may be performing using equipment,such as a MUEGGE SU-8 Stripping Tool MA 3000D-161 BB from MUEGGE GMBH ofReichelsheim, Germany.

Further Comments and Conclusions

Some embodiments may employ diffusion bonding or the like to enhanceadhesion between successive layers of material. Various teachingsconcerning the use of diffusion bonding in electrochemical fabricationprocesses are set forth in U.S. patent application Ser. No. 10/841,384which was filed May 7, 2004 by Cohen et al., now abandoned, which isentitled “Method of Electrochemically Fabricating Multilayer StructuresHaving Improved Interlayer Adhesion” and which is hereby incorporatedherein by reference as if set forth in full. This application is herebyincorporated herein by reference as if set forth in full.

Though the embodiments explicitly set forth herein have consideredmulti-material layers to be formed one after another. In someembodiments, it is possible to form structures on a layer-by-layer basisbut to deviate from a strict planar layer on planar layer build upprocess in favor of a process that interlaces material between thelayers. Such alternative build processes are disclosed in U.S.application Ser. No. 10/434,519, filed on May 7, 2003, now U.S. Pat. No.7,252,861, entitled Methods of and Apparatus for ElectrochemicallyFabricating Structures Via Interlaced Layers or Via Selective Etchingand Filling of Voids. The techniques disclosed in this referencedapplication may be combined with the techniques and alternatives setforth explicitly herein to derive additional alternative embodiments. Inparticular, the structural features are still defined on aplanar-layer-by-planar-layer basis but material associated with somelayers are formed along with material for other layers such thatinterlacing of deposited material occurs. Such interlacing may lead toreduced structural distortion during formation or improved interlayeradhesion. This patent application is herein incorporated by reference asif set forth in full.

While various specific embodiments and some variations have been setforth above, numerous other variations are possible. Some suchvariations may involve the addition of some steps or operations from oneembodiment into another embodiment or the replacement of steps in oneembodiment by steps from a different embodiment. In some embodimentvariations and implementations, structural materials may beelectrodepositable materials such as nickel, nickel-cobalt, nickelmanganese, nickel phosphor, silver, rhodium, palladium, gold, and/orpalladium while in other embodiments other metals, semiconductormaterials, or dielectrics may be used which may or may not beelectrodepositable. In some embodiments sacrificial material may includeone or more metals, such as copper or tin in addition to variousdielectrics. In some embodiments material deposition may occur by one ormore of electroplating, electroless plating, physical vapor deposition,chemical vapor deposition, spreading, spraying, ink jetting, extruding,fling coating, and the like. In some embodiments additional steps may beused to provide enhanced or improved part formation such as for example,cleaning steps, surface activation steps, alloying steps, diffusionbonding steps, heat treating steps, process tracking steps, temperature,or atmosphere control steps, and the like. In some embodiments, materialmay be supplied in the form of sheets or powders. In some embodiments,different layers may have different thickness, more than two structuralmaterials may be deposited on any given layer or on different layersand/or more than one sacrificial material may be used on any given layeror on different layers.

In some embodiments, tracking of failed parts may occur manually, orautomatically (e.g. by computer/program controlled inspection/testhardware, optics, and/or analysis or comparison methods). For example,parts on a wafer may be examined under manual or computer control of anencoder (X and Y) tracked microscope reticle and when bad parts areidentified, a position may be read and manually logged or alternatively,a button may be pressed or other command may be issued that causes thecurrent microscope X & Y position to be automatically recorded as partof a list of bad structures or part positions. The recorded positionsmay be identified with specific parts and then specific cutting ortethering positions identified.

In some embodiment variations, a computer running a program may be usedto correlate the defect locations with the affected parts on the build.In some embodiment variations, part modification locations (e.g. cuttingor ablation locations) may be targeted using supplied coordinate dataonly, coordinate data in combination with optical recognition softwareand a camera that is viewing the build, feedback between positioningmovements, commanded modification locations and detected modifications.In some embodiments, the processes set forth herein may be implementedvia multiple independent machines (some or all of which may be manuallyoperated or some or all of which may be computer controlled by programsoperating on user supplied data and/or information generated by othersystem components). In some implementations a single multifunctioncomputer controlled apparatus may be used. In some embodimentvariations, modifications may take a number of forms includingunambiguously marking the good parts or the bad parts, destroyingsuspected bad parts or otherwise selected parts (e.g. cutting them inhalf, in thirds, in fourths, etc.), completely ablating or machiningthem into non-existence, creating obvious damage that will provide clearand unambiguous indications of which parts are bad (e.g. slotting tips,putting holes in parts, removing any mounting or alignment features,etc.).

The patent applications and patents set forth below are herebyincorporated by reference herein as if set forth in full. The teachingsin these incorporated applications can be combined with the teachingsset forth directly in these pages and drawings in many ways: Forexample, enhanced methods of producing structures may be derived fromsome combinations of teachings, enhanced structures may be obtainable,enhanced apparatus may be derived, devices or components may beobtainable (e.g. from various combinations of structural features ofdifferent embodiments or various combinations of materials that giveenhanced reliability, that promote easy of assembly, that provideenhanced functionality, or that provide quicker, less expensive, or moreautomated device fabrication, testing, and the like.

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Though various portions of this specification have been provided withheaders, it is not intended that the headers be used to limit theapplication of teachings found in one portion of the specification fromapplying to other portions of the specification. For example, it shouldbe understood that alternatives acknowledged in association with oneembodiment, are intended to apply to all embodiments to the extent thatthe features of the different embodiments make such applicationfunctional and do not otherwise contradict or remove all benefits of theadopted embodiment. Various other embodiments of the present inventionexist. Some of these embodiments may be based on a combination of theteachings set forth directly herein with various teachings incorporatedherein by reference.

In view of the teachings herein, many further embodiments, alternativesin design and uses of the embodiments of the instant invention will beapparent to those of skill in the art. As such, it is not intended thatthe invention be limited to the particular illustrative embodiments,alternatives, and uses described above but instead that it be solelylimited by the claims presented hereafter.

We claim:
 1. A batch method for forming a plurality of three-dimensionalstructures simultaneously, comprising: (A) forming a plurality ofsuccessively formed multi-material layers, wherein each successivemulti-material layer comprises at least two materials and is formed onand adhered to a previously formed multi-material layer, wherein one ofthe at least two materials is a structural material and the other of theat least two materials is a sacrificial material, and wherein eachsuccessive multi-material layer defines a successive cross-section ofthe plurality of three-dimensional structures, and wherein the formingof each of the plurality of successive multi-material layers comprises:(i) depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; (iii) planarizing the first andsecond materials to set a boundary level for the multi-material layer;and wherein the forming of a given one or more of the plurality ofsuccessively formed multi-material layers comprises: (i) applying afirst patternable mold material (PMM), a portion of which forms asacrificial material portion of the multi-material layer; (ii)patterning the first PMM to form a first pattern of sacrificialmaterial; (iii) depositing a structural material in openings in thefirst pattern of sacrificial material; (iv) planarizing the sacrificialmaterial and the structural material to set a boundary level for thegiven multi-material layer; and (B) after the forming of the pluralityof successive multi-material layers, separating at least a portion ofthe sacrificial material from multiple multi-material layers of thestructural material via an etching operation that is limited tonon-ionized radical etching, wherein after formation of a selectedmulti-material layer but prior to the completion of the formation of allmulti-material layers at least one intermediate release operation isperformed to release at least selected regions of the sacrificialmaterial from multiple multi-material layers including at least onereentrant region existing under the selected layer and thereafterdepositing a second sacrificial material and thereafter forming at leastone additional multi-material layer above the selected layer and thesecond sacrificial material.
 2. The method of claim 1 wherein the PMM isa material selected from the group consisting of: (1) a polymer, (2) aphotoresist, (3) a dielectric, and (4) a conductive epoxy.
 3. The methodof claim 1 wherein the PMM is coated, at least in part, with aconductive material prior to depositing the structural material for thegiven one of the plurality of multi-material layers.
 4. The method ofclaim 3 wherein the conductive material provided in preparation fordepositing the structural material comprises an adhesion layer.
 5. Themethod of claim 1 wherein the second sacrificial material does not fillall reentrant features where the first sacrificial material was removed.6. The method of claim 5 wherein the second sacrificial material iseasier to remove than the first sacrificial material by the radicaletching.
 7. The method of claim 5 wherein the structural material of theselected layer provides a feature selected from the group consisting of(1) a reentrant feature with an R-factor greater than 5, (2) a reentrantfeature with a R-factor greater than 10, (3) a reentrant feature with aR-factor greater than 20, and (4) a reentrant feature with a R-factorgreater than
 50. 8. The method of claim 5 wherein a multi-material layerabove the selected layer contains structural material that provides afeature selected from the group consisting of (1) a reentrant featurewith an R-factor greater than 5, (2) a reentrant feature with a R-factorgreater than 10, (3) a reentrant feature with a R-factor greater than20, and (4) a reentrant feature with a R-factor greater than
 50. 9. Themethod of claim 1 wherein the structure includes at least one reentrantfeature having an R-factor selected from the group consisting of (1)greater than 5, (2) greater than 10, (3) greater than 20, and (4)greater than
 50. 10. The method of claim 1 wherein the etching occurs ina sub-atmospheric pressure chamber.
 11. The method of claim 1 wherein atleast one additional cleaning step is performed after the etching. 12.The method of claim 1 wherein the structural material comprises at leastone metal.
 13. The method of claim 12 wherein the structural material isselected from the group consisting of (1) at least two different metals,(2) at least two different metals deposited on two differentmulti-material layers, and (3) at least two different metals depositedas part of the same multi-material layer.
 14. The method of claim 1wherein the sacrificial material on at least a portion of the pluralityof multi-material layers comprises SU-8.
 15. The method of claim 1wherein the formation of a particular multi-material layer includesformation of a seed layer selected from the group consisting of (1)formation of a non-planar seed layer when structural material formingpart of the particular multi-material layer overlays material other thanmetal structural material on an immediately preceding multi-materiallayer and (2) formation of a planar seed layer when structural materialforming part of the particular multi-material layer overlays materialother than metal structural material on an immediately precedingmulti-material layer.
 16. The method of claim 1 wherein at least one ofthe depositing steps comprises electroplating.
 17. The method of claim 1wherein the given multi-material layer comprises a number ofmulti-material layers selected from the group consisting of: (1) atleast two multi-material layers; (2) at least three multi-materiallayers; (3) a plurality of multi-material layers but less than allmulti-material layers, (4) at least one half of the multi-materiallayers, (5) at least two thirds of the multi-material layers; and (6)all of the multi-material layers.
 18. The method of claim 1 wherein thestructures are selected from the group consisting of (1) horizontally orvertically complex multilayer three-dimensional structures, (2)horizontally or vertically moderately complex multilayerthree-dimensional structures, and (3) horizontally or vertically highlycomplex multilayer three-dimensional structures.
 19. A method for thebatch formation of a plurality of multi-layer structures, comprising:successively forming a plurality of multi-material layers, wherein eachsuccessive multi-material layer is formed on and adhered to a precedingmulti-material layer, and wherein each of the plurality ofmulti-material layers comprises both a structural material and asacrificial material; and after forming the plurality of adheredmulti-material layers, removing the sacrificial material from theplurality of plurality of multi-material layers to leave a multi-layerstructure comprising the structural material, wherein the multi-layerstructure comprises at least one reentrant feature, wherein thesacrificial material comprises an organic material that is removed by anetching operation that is limited to non-ionized radical etching,wherein after formation of a selected multi-material layer but prior tothe completion of the formation of all multi-material layers at leastone intermediate release operation is performed to release at leastselected regions of the sacrificial material from multiplemulti-material layers including at least one reentrant region existingunder the selected layer and thereafter depositing a second sacrificialmaterial and thereafter forming at least one additional multi-materiallayer above the selected layer and the second sacrificial material. 20.The method of claim 19 wherein the at least one reentrant feature has anR-factor selected from the group consisting of (1) greater than 5, (2)greater than 10, (3) greater than 20, and (4) greater than 50.